Hydrotreating catalysts prepared from hydrogels

ABSTRACT

This invention relates to a process for preparing highly active hydrotreating catalysts prepared by incorporating a metals solution containing an element selected from the group consisting of molybdenum, tungsten and mixtures thereof, an element selected from the group consisting of nickel, cobalt and mixtures thereof, and a stabilizing amount of phosphorus into an alumina hydrogel support. The final calcined catalysts have surface areas greater than about 300 m 2  /g, crush strengths greater than about 20 lbs and more than about 80% of their pore volume in pores having diameters less than about 50 Å.

FIELD OF THE INVENTION

This invention relates to a process for preparing highly active aluminahydrogel-derived catalysts.

BACKGROUND OF THE INVENTION

In the catalytic processing of petroleum feedstocks, it is oftendesirable to alter the pore structure of the catalyst in order toaccommodate different types of feeds. For example, when processingfeedstocks of high metals content, the metals tend to deposit rapidly onthe catalyst surface and plug the pores of conventional hydroprocessingcatalysts, resulting in a loss of catalytic activity for sulfur andnitrogen removal. To facilitate the diffusion of large components intoand out of the catalyst and to prevent surface deposits of coke andmetals, large pore diameters are required. On the other hand, whenprocessing feedstocks with no metals or with low metals contents, it maybe technically and economically desirable to use narrow-pore catalysts.For purposes of denitrification, narrow-pore catalysts have higheractivities and longer lives than catalysts containing large pores whichtend to deactivate quickly.

Related cases include co-pending applications Ser. No. 924,091, filedOct. 28, 1986, and Ser. No. 924,092 filed Oct. 28, 1986, which aredirected to catalysts prepared by the incorporation of metals solutionsinto hydrogels.

SUMMARY OF THE INVENTION

The present invention relates to a process for the preparation ofhydrotreating catalysts containing an element selected from the groupconsisting of molybdenum, tungsten and mixtures thereof, an elementselected from the group consisting of nickel, cobalt and mixturesthereof, and phosphorus incorporated into an alumina hydrogel-derivedsupport. The catalyst is prepared by a process which comprises:

b(a) titrating an aqueous solution of an acid aluminum salt with anaqueous solution of a basic aluminum compound, thereby forming aprecipitate,

(b) aging the precipitate at a temperature ranging from about 20° C. toabout 90° C. for at least about 15 minutes at a pH ranging from about11.0 to about 12.5,

(c) washing the precipitate,

(d) mixing the precipitate with a solution containing solubilized saltsof a heavy metal selected from the group consisting of molybdenum,tungsten and mixtures thereof, an element selected from the groupconsisting of nickel, cobalt and mixtures thereof, and aphosphorus-containing compound in an amount from about 0.2 to about 1.5moles of phosphorus per mole of heavy metal at a pH in the range betweenabout 4.0 and about 8.0 and a temperature in the range between about 25°C. and about 100° C. until adsorption of the metal salts onto the gel issufficient to yield a final catalyst having from about 1% w to about 5%w nickel and/or cobalt and from about 8% w to about 32% w heavy metal,

(e) extruding the product of step (d), and

(f) drying and calcining the product of step (e) at a temperatureranging from about 300° C. to about 900° C.

It has been found that catalysts prepared from hydrogels aged at highpHs have physical properties better than catalysts prepared fromhydrogels aged at lower pHs as well as catalysts prepared byconventional impregnation techniques. Two of the major advantages of thehydrogel route are higher metals utilization and lower costs of catalystmanufacture. The catalysts prepared according to the invention have highsurface areas, greater than about 300 m² /g; high flat plate crushstrengths, greater than about 20 lbs; and substantial portions, greaterthan about 80%, of their pores with diameters less than about 50 Å.These catalysts are particularly useful for hydrotreating applications.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the process of the instant invention, a highly active hydrotreatingcatalyst is prepared by incorporating a metals solution containing anelement selected from the group consisting of molybdenum, tungsten andmixtures thereof, an element selected from the group consisting ofnickel, cobalt and mixtures thereof, and a phosphorus-containingcompound into an alumina hydrogel-derived support prepared by titratingan aqueous solution of an acid aluminum salt with an aqueous solution ofa basic aluminum compound.

The alumina hydrogel can be prepared by titrating an aqueous solution ofone or more aluminum salt(s) with an appropriate acidic or basicmaterial or solution to cause precipitation of the phosphated aluminagel. One skilled in the art will recognize that the alumina gel can beprepared by titrating an acidic aluminum salt such as, for example,aluminum sulfate, aluminum nitrate or aluminum chloride, in aqueoussolution with a basic precipitating medium such as, for example, sodiumhydroxide or ammonium hydroxide, or, by titrating an alkali metalaluminate such as, for example, sodium aluminate or potassium aluminate,in aqueous solution with an acidic precipitating medium such as, forexample, hydrochloric acid or nitric acid. One skilled in the art willrecognize that the adjustment of the pH of an aluminum-containingsolution to between about 5.5 and about 10.0 will result inprecipitation of the aluminum as aluminum hydroxide or hydrated aluminumoxide.

In a preferred embodiment, the alumina hydrogel is prepared by titratingan aqueous solution of an alkali metal aluminate and an aqueous solutionof acid aluminum salt to cause precipitation of the alumina gel.Suitable acidic aluminum salts include aluminum sulfate, aluminumnitrate and aluminum chloride. A preferred species is aluminum chloride.Suitable alkali metal aluminates are sodium aluminate and potassiumaluminate. The precipitation can be carried out by adding an aqueoussolution of the basic aluminum species to an aqueous solution of theacidic aluminum species or the procedure can be reversed by adding anaqueous solution of the acidic aluminum species to an aqueous solutionof the basic aluminum species (referred to as "sequentialprecipitation"). Preferably, the precipitation in the instant inventionis carried out by simultaneously adding the acid aluminum species andthe basic aluminum species to cause precipitation of the hydrogel(referred to as "simultaneous precipitation").

The temperature and pH of the precipitation are important variables inthe preparation of the aluminas into which metals solutions can beincorporated to form hydrotreating catalysts with desirable physicalqualities. Changes in precipitation temperatures and pHs result inchanges in porosities. In the instant invention, a precipitationtemperature typically ranges from about 20° C. to about 90° C., andpreferably from about 50° C. to about 85° C., and a precipitation pHtypically ranges between about 5.5 and about 10.0, preferably betweenabout 5.5 and about 8.0, and more preferably between about 6.0 and about7.5. The length of time required for the precipitation step is notcritical. However, the maximum rate of addition of the acid aluminumspecies and the basic aluminum species is fixed by the rate at which thetwo streams can be mixed and the pH and temperature of the system can beeffectively controlled.

After the precipitation step is completed, the pH of the slurry isadjusted by the addition of the basic aluminate solution to fall in therange from about 11.0 to about 12.5 preferably about 11.0 to about 12.0,most preferably about 11.5 to about 12.0, and aged at a temperature inthe range from about 20° C. to about 90° C., preferably about 50° C. toabout 85° C. for at least about 15 minutes. An upper limit on the lengthof time for aging is not critical and is normally determined byeconomical considerations. Aging times will typically range from about0.1 to about 10 hours, preferably from about 0.25 to about 5 hours, andmore preferably from about 0.25 to about 1 hour. In general, aluminaswith acceptable properties are produced by holding the aging temperatureequal to the precipitation temperature. The aging pH, however, iscritical. Products with acceptable pore size distributions are preparedonly when the aging pH is between about 11.0 and about 12.5, andpreferably between about 11.0 and about 12.0. Compounds prepared atlower pH values contain primarily macropores. The products formedcontaining macropores have unacceptably low crush strengths. Aging atexcessively high pHs will result in dissolution of the alumina gel.

After aging, the slurry is washed and filtered in routine fashion toremove substantially all the salts formed during the precipitation ofthe hydrogel which can be removed by washing. The preferred solvent forwashing is water although other solvents such as lower alkanols may beutilized.

After washing, the hydrogel is reslurried with a solution containingsolubilized salts of a heavy metal selected from the group consisting ofmolybdenum, tungsten and mixtures thereof, and an element selected fromthe group consisting of nickel, cobalt and mixtures thereof, and aphosphorus-containing compound an amount of from about 0.2 to about 1.5moles of phosphorus per mole of sufficient to deposit on the finalcatalyst from about 1% w to about 5% w nickel and/or cobalt and fromabout 8% w to about 18% w molybdenum or about 10% w to about 32% wtungsten. When mixtures of molybdenum and tungsten are utilized, thefinal catalyst contains from about 8% w to about 32% w molybdenum and/ortungsten. Alternatively, the solution may contain amounts of nickeland/or cobalt and molybdenum or tungsten in excess of that required todeposit the aforesaid amounts of metals, which excess may be removed bywashing following the reslurry step. A typical metals solution can beprepared by combining a molydbenum solution with a nickel and/or cobaltsolution. A phosphorus-containing compound is typically added to thenickel and/or cobalt solutions in order to prevent formation of unstablenickel and/or cobalt/molybdenum or nickel and/or cobalt/tungstencomplexes when the solutions are combined. As used herein, the term "aphosphorus-containing compound" is generic and refers to onephosphorus-containing compound as well as more than onephosphorus-containing compound. The phosphorus-containing compound isgenerally selected from the group consisting of phosphoric acid, aphosphate salt or mixtures thereof. Suitable phosphate salts includealkali metal phosphate, alkali metal hydrogen phosphate, ammoniumphosphate and ammonium hydrogen phosphate.

The molybdenum solution consists of a water-soluble source of molybdenumsuch as ammonium heptamolybdate or ammonium dimolybdate dissolved inwater. Hydrogen peroxide may also be used to aid in solution preparationin some cases. A preferred method for preparing the molybdenum solutionconsists of adding hydrogen peroxide to the solution in the range ofabout 0.1 to about 1.0 mole of hydrogen peroxide per mole of molybdenum.Optionally, a suitable soluble amine compound such as monoethanolamine,propanolamine or ethylenediamine may be added to the molybdenum solutionin order to aid in stabilization of the solution.

The tungsten solution typically consists of ammonium metatungstatedissolved in water. A preferred method for preparing the tungstensolution consists of adding hydrogen peroxide to the solution in therange of about 0.1 to about 1.0 mole of hydrogen peroxide per mole oftungsten. In addition, a suitable soluble amine compound such asmonoetholamine, propanolamine or ethylenediamine may be added to thetungsten solution in order to aid in stabilization of the solution.

The nickel solution consists of nickel salts dissolved in water and aphosphorus-containing compound. A wide range of nickel compounds aresuitable, such as nickel nitrate, nickel acetate, nickel formate, nickelsulfate, nickel oxide, nickel phosphate, nickel carbonate, nickelchloride, and nickel hydroxide. Two compounds that are especially usefulare nickel nitrate and nickel carbonate.

The cobalt solution consists of cobalt salts dissolved in water and aphosphorus-containing compound. A wide range of cobalt compounds aresuitable, such as cobalt nitrate, cobalt hydroxide, cobalt acetate,cobalt oxalate, or cobalt oxide. The preferred cobalt compound is cobaltnitrate.

The temperature and pH of the reslurry step are both important variablesin the preparation of hydrogel-derived catalysts which have acceptabledensities and porosities. In general, high temperatures in the reslurrystep result in lower density catalysts. The pH of the reslurry step,however, is critical to the formation of catalysts having the desiredproperties. The reslurry of the hydrogel support with the metalssolution is carried out at a pH in the range between about 4.0 and about8.0, preferably between about 4.0 and about 6.0, adjusting to these pHranges by adding, if necessary, acid or base to the hydrogel, the metalssolution and/or the mixture of the slurry and the metals solution, and atemperature in the range between about 25° C. and about 100° C.,preferably between about 25° C. and about 80° C., until adsorption ofthe metals salts onto the gel is sufficient to yield a final calcinedcatalyst having from about 1% w to about 5% w nickel and/or cobalt andfrom 8% w to about 18% w molybdenum or from about 10% w to about 32% wtungsten. Reslurry pHs less than about 4.0 result in dissolution of thealumina gel and reslurry pHs greater than about 8.0 result in failure ofthe molybdenum or tungsten to adsorb onto the gel. Typically, the timesfor reslurry will range from about 0.5 to about 2 hours. Optionally, theresulting material can be washed to remove unadsorbed metals andfiltered in routine fashion.

Following the reslurry step, the material may be extruded and then driedand calcined; dried, mulled with addition of water, extruded or pelletedand calcined; or partially dried, extruded or pelleted, dried morecompletely and calcined. Drying is accomplished by conventional means.It may be carried out by forced draft drying, vacuum drying, air dryingor similar means. Drying temperatures are not critical and depend uponthe particular means utilized for drying. Drying temperatures willtypically range from about 50° C. to about 150° C.

In a preferred embodiment, the material is extruded and then dried.Alternatively, the material may be extruded after drying to the properloss on ignition (1.0I). However, to facilitate extrusion, organicbinders and/or lubricants may be added prior to extrusion.

After drying, the material is calcined to produce the finished catalyst.The material may be calcined in any atmosphere, reducing, oxidizing orneutral, although air is preferred. However, if binders and/orlubricants are used the material is heated in an oxygen-containingatmosphere, preferably air, in order to burn out the binders andlubricants. Calcining temperatures will typially range from about 300°C. to about 900° C. Burn-out temperatures will depend on theconcentration of oxygen in the burn-out atmosphere as well as theburn-out time involved. Typically, burn-out temperatures will range fromabout 300° C. to about 900° C. Drying, calcining and burn-out may becombined in one or two steps. Most frequently the calcining and/orburn-out steps are combined using an oxygen-containing atmosphere.

Certain other processing steps may be incorporated into theabove-described procedure without deviating from the scope and intent ofthis invention. For example, prior to the complete drying of thecatalyst, it may be extruded and then dried more completely, followed bycalcination.

The final catalysts are found to have surface areas greater than about300 m² /g, pore volumes ranging from about 0.4 to about 1.2 cc/g andwith at least 80% of its pore volume in pores having diameters less thanabout 50 Å. Crush strengths are greater than about 20 lbs. In general,the metals contents of the final catalysts range from about 1% w toabout 5% w, preferably from about 2.5% w to about 4% w nickel and/orcobalt, and from about 8% w to about 18% w, preferably about 10% w toabout 14% w molybdenum or about 10% w to about 32% w, preferably about18% w to about 26% w tungsten.

The catalysts prepared in the instant invention can be suitably appliedto hydrocarbon conversion processes such as catalytic cracking,hydrocracking, hydrotreating, isomerization, hydrogenation,disproportionation, dehydrogenation, oligomerization, alkylation,dealkylation and the like.

The catalysts of the instant invention are most commonly employed inhydrotreating feedstocks ranging in volatilities from napthas to flasheddistillates. Reaction temperatures will typically range from about 300°F. to about 850° F., preferably from about 500° F. to about 775° F.Reaction pressures are generally within the range of about 200 psig toabout 2500 psig, preferably from about 600 psig to about 1500 psig.Reactions are conducted at liquid hourly spaced velocities within therange of about 0.1 to about 10 reciprocal hour.

Multiple uses of these feedstock after treating with the catalysts ofthis invention are possible. Depending on the particular feedstockstreated, suitable uses can include conversion unit feedstock or finishedproducts such as gasoline, diesel, airline turbine fuel, furnace oilsand solvents.

The process for preparing the catalysts of the instant invention will befurther described below by the following examples which are provided forillustration and which are not to be construed as limiting theinvention.

EXAMPLE 1

Seven hundred and forty grams of reagent grade sodium aluminate wereadded to 1000 grams of water which was then heated to 60° C. in order toeffect dissolution of the materials. Five hundred and forty-four gramsof aluminum chloride hexahydrate were added to 760 grams of water. Bothsolutions were cooled to slightly less than 60° C. and placed indropping funnels.

Five thousand grams of water were added to a 10 liter stainless steelbucket equipped with a pH meter, thermometer and stirrer, to serve asthe heel. After the pH of the heel was adjusted to 7.0 using the sodiumaluminate solution, the two solutions in the dropping funnels were addedsimultaneously to the well-stirred bucket, maintaining a precipitationpH of 7. A total of 1740 grams of sodium aluminate solution and 1216grams of aluminum chloride solution were used to effect the titration.After these quantities of reagents had been used, the final aging pH ofthe solution rose to between 11.0 and 12.0. The solution was aged forone hour at 60° C. The resulting material was filtered and washed in twolarge Buchner funnels with about 50 liters of water. The excess waterfrom the wet filter cake was removed by vacuum. The hydrogel was thendivided into two equal portions.

The following solutions were then prepared. 91.71 grams of nickelnitrate as hexahydrate was mixed with 64.59 grams of 85% phosphoric acidand diluted to 1000 milliliters with water. An additional solution of136.17 grams of ammonium heptamolybdate and 21.21 grams of 30% hydrogenperoxide were diluted to 1000 milliters with water. The two solutionswere combined slowly with stirring and one portion of the hydrogel wasadded and reslurried with one-half of the solution at 80° C. for twohours at a pH of 5.0. At the end of two hours, the slurry was filteredand washed with two liters of water. The excess water from the slurrywas again removed by vacuum. The wet gel was then extruded using asmall, hand-held extruder using a 0.156" cylindrical die, driedovernight at 120° C. and calcined in air at 510° C. The properties ofthe catalyst are listed in Tables I and II.

COMPARATIVE EXPERIMENT A

A catalyst was prepared according to Example 1 except that the agingstep was carried out at a pH of 10.0. The properties of the catalyst arelisted in Tables I and II.

COMPARATIVE EXPERIMENT B

A catalyst was prepared using a conventional dry pore volumeimpregnation technique. A solution suitable for impregnating a gammaalumina carrier was prepared as follows. A first solution was made byadding 19.39 grams of nickel nitrate and 16.18 grams of phosphoric acidto 5 milliliters of water which solution was then heated to 40° C. andstirred in order to effect dissolution of the materials. A secondsolution was prepared by mixing 5.5 milliliters of 30% hydrogenperoxide, 30 milliliters of distilled water and 35.20 grams of ammoniumheptamolybdate. The mixture was then heated to 40° C. and stirred untilall solids were dissolved. When both solutions were at or near ambienttemperature, the second solution was slowly added to the first solutionwhile stirring. After cooling and diluting with water to the total porevolume of the support, the solution was added to the gamma aluminasupport in several small portions with intermediate agitations. Theimpregnated support was further agitated about 5 minutes, dried for 2hours at 400°0 F. and calcined in air for 2 hours at 900° F. Theproperties of the catalyst are listed in Tables I and II.

                                      TABLE I                                     __________________________________________________________________________    Catalyst Properties                                                                             COMPARATIVE                                                                             COMPARATIVE                                                  EXAMPLE 1                                                                            EXPERIMENT A                                                                            EXPERIMENT B                                      __________________________________________________________________________    Aging pH.sup.(a)                                                                         11.0-12.0                                                                            10.0      --                                                Density g/cc.sup.(b)                                                                     0.72   0.26      0.86                                              Reslurry pH.sup.(c)                                                                      5.0    5.0       --                                                N.sub.2 Surface                                                                          428.0  427.0     186.0                                             Area m.sup.2 /g.sup.(d)                                                       N.sub.2 Pore                                                                             0.54   1.39      --                                                Volume cc/g.sup.(e)                                                           Flat Plate Crush                                                                         24.0   8.0       17.5                                              Strength lbs..sup.(f)                                                         % wt. Nickel.sup.(g)                                                                     1.2    2.4       2.7                                               % wt. Molybdenum.sup.(h)                                                                 11.8   10.5      13.2                                              % wt. Phosphorus.sup.(i)                                                                 3.4    3.7       3.0                                               __________________________________________________________________________     .sup.(a) Measured using an Orion 231 pH meter and Orion electrodes.           .sup.(b) 209 cc volume fully settled in a graduated cup and weighed.          .sup.(c) Measured using an Orion 231 pH meter and Orion electrodes.           .sup.(d) BET, by nitrogen adsorption/desorption, Micromeritics Digisorb       2500 Instrument.                                                              .sup.(e) By nitrogen adsorption, Micromeritics Digisorb 2500 Instrument.      .sup.(f) Flat plate, single pellet, extrudate approximately 5 mm in           length.                                                                       .sup.(g) Weight percent determined by neutron activation analysis or          atomic absorption spectroscopy.                                               .sup.(h) Weight percent determined by neutron acitvation analysis or          atomic absorption spectroscopy.                                               .sup.(i) Weight percent determined by neutron activation analysis or          atomec absorption spectroscopy.                                          

                  TABLE II                                                        ______________________________________                                        Catalyst Pore Size Distributions                                                                 COMPAR-      COMPAR-                                       Hg Pore.sup.(j)    ATIVE EX-    ATIVE EX-                                     Size Dist                                                                             EXAMPLE 1  PERIMENT A   PERIMENT B                                    ______________________________________                                        <50 ang 86.3       0.8          1.7                                           50-70 ang                                                                             4.8        0.8          15.3                                          70-100 ang                                                                            3.0        11.9         29.3                                          100-150 ang                                                                           2.8        9.6          40.3                                          150-350 ang                                                                           2.5        12.5         5.1                                           >350 ang                                                                              0.7        64.4         8.4                                           ______________________________________                                         .sup.(j) Determined by mercury intrusion, to 60,000 psi using a               Micromeritics Autopore 9210, using a 130° contact angle and 0.473      N/m surface tension of mercury. Numbers listed are percent pore volume.  

I claim as my invention:
 1. A process for preparing highly activehydrotreating catalysts having surface areas above about 300 m² /g andat least about 80% of the pore volume in pores having diameters lessthan about 50 Å, which process comprises:(a) precipitating an aqueoussolution of one or more aluminum salt(s) by adjusting the pH of saidsolution to a range between about 5.5 and about 10.0 and a temperaturein the range between about 20° C. and about 90° C., (b) aging theprecipitate at a temperature ranging from about 20° C. to about 90° C.for at least about 15 minutes at a pH ranging from about 11.0 to about12.5, (c) washing the precipitate, (d) mixing the precipitate with asolution containing solubilized salts of a heavy metal selected from thegroup consisting of molybdenum, tungsten and mixtures thereof and anelement selected from the group consisting of nickel, cobalt andmixtures thereof, and a phosphorus-containing compound in an amount offrom about 0.2 to about 1.5 moles of phosphorus per mole of heavy metalat a pH in the range between about 4.0 and about 8.0 and a temperaturein the range between about 25° C. and about 100° C. until adsorption ofthe metal salts onto the gel is sufficient to yield a final catalysthaving from about 1% w to about 5% w nickel and/or cobalt and from about8% w to about 32% w heavy metal, (e) extruding the product of step (d),and (f) drying and calcining the product of step (e) at a temperatureranging from about 300° C. to about 900° C.
 2. The process of claim 1wherein the precipitation is carried out at a pH in the range betweenabout 5.5 and about 8.0.
 3. The process of claim 1 wherein theprecipitation is carried out at a temperature between about 50° C. andabout 85° C.
 4. The process of claim 1 wherein the aging pH is in therange between about 11.0 and about 12.0.
 5. The process of claim 1wherein step (d) is carried out at a pH in the range between about 4.0and about 6.0.
 6. The process of claim 1 wherein saidphosphorus-containing compound is selected from the group consisting ofphosphoric acid, a phosphate salt and mixtures thereof.
 7. The processof claim 1 wherein said solution in step (d) contains solubilized saltsof nickel and molybdenum.
 8. The process of claim 7 wherein saidcatalyst contains from about 2.5% w to about 4% w nickel and from about8% w to about 18% w molybdenum.
 9. The process of claim 1 wherein saidsolution in step (d) contains solubilized salts of cobalt andmolybdenum.
 10. The process of claim 9 wherein said catalyst containsfrom about 2.5% w to about 4% w cobalt and from about 8% w to about 18%w molybdenum.
 11. A process for preparing highly active hydrotreatingcatalysts having surface areas above about 300 m² /g and at least about80% of the pore volume in pores having diameters less than about 50 Å,which process comprises:(a) titrating an aqueous solution of an acidaluminum salt with an aqueous solution of a basic aluminum compound at apH in the range between about 5.5 and about 10.0 and a temperature inthe range between about 20° C. and about 90° C., thereby forming aprecipitate, (b) aging the precipitate at a temperature ranging fromabout 20° C. to about 90° C. for at least about 15 minutes at a pHranging from about 11.0 to about 12.5, (c) washing the precipitate, (d)mixing the precipitate with one or more solution(s) containingsolubilized salts of a heavy metal selected from the group consisting ofmolybdenum, tungsten and mixtures thereof, and an element selected fromthe group consisting of nickel, cobalt and mixtures thereof, and aphosphorus-containing compound in an amount of from about 0.2 to about1.5 moles of phosphorus per mole of heavy metal at a pH in the rangebetween about 4.0 and about 8.0 and a temperature in the range betweenabout 25° C. and about 100° C. until adsorption of the metal salts ontothe gel is sufficient to yield a final catalyst having from about 1% wto about 5% w nickel and/or cobalt and from about 8% w to about 32% wheavy metal, (e) extruding the product of step (d), and (f) drying andcalcining the product of step (e) at a temperature ranging from about300° C. to about 900° C.
 12. The process of claim 11 wherein theprecipitation is carried out at a pH in the range between about 5.5 andabout 8.0.
 13. The process of claim 11 wherein the precipitation iscarried out at a temperature between about 50° C. and about 85° C. 14.The process of claim 11 wherein the aging pH is in the range betweenabout 11.0 and about 12.0.
 15. The process of claim 11 wherein step (d)is carried out at a pH in the range between about 4.0 and about 6.0. 16.The process of claim 11 wherein said phosphorus-containing compound isselected from the group consisting of phosphoric acid, a phosphate saltand mixtures thereof.
 17. The process of claim 11 wherein said solutionin step (d) contains solubilized salts of nickel and molybdenum.
 18. Theprocess of claim 17 wherein said catalyst contains from about 2.5% w toabout 4% w nickel and from about 8% w to about 18% w molybdenum.
 19. Theprocess of claim 11 wherein said solution in step (d) containssolubilized salts of cobalt and molybdenum.
 20. The process of claim 19wherein said catalyst contains from about 2.5% w to about 4% w cobaltand from about 8% w to about 18% w molybdenum.
 21. A process forpreparing highly active hydrotreating catalysts having surface areasabove about 300 m² /g and at least about 80% of the pore volume in poreshaving diameters less than about 50 Å, which process comprises:(a)titrating an aqueous solution of an acid aluminum salt selected from thegroup consisting of aluminum sulfate, aluminum nitrate and aluminumchloride, with an aqueous solution of a basic aluminum compound selectedfrom the group consisting of sodium aluminate and potassium aluminate,at a pH in the range between about 5.5 and about 8.0 and a temperaturein the range between about 20° C. and about 90° C., thereby forming aprecipitate, (b) aging the precipitate at a temperature ranging fromabout 20° C. to about 90° C. for at least about 15 minutes at a pHranging from about 11.0 to about 12.0, (c) washing the precipitate, (d)mixing the precipitate with one or more solution(s) containingsolubilized molybdate or dimolybdate salts and nickel salts, andphosphoric acid in an amount of from about 0.2 to about 1.5 moles ofphosphorus per mole of molybdenum at a pH in the range between about 4.0and about 6.0 and a temperature in the range between about 25° C. andabout 100° C. until adsorption of the metal salts onto the gel issufficient to yield a final catalyst having from about 2.5% w to about4% w nickel and from about 10% w to about 14% w molybdenum (e) extrudingthe product of step (d), and (f) drying and calcining the product ofstep (e) at a temperature ranging from about 300° C. to about 900° C.22. A process for preparing highly active hydrotreating catalysts havingsurface areas above about 300 m² /g and at least about 80% of the porevolume in pores having diameters less than about 50 Å, which processcomprises:(a) titrating an aqueous solution of an acid aluminum saltselected from the group consisting of aluminum sulfate, aluminum nitrateand aluminum chloride, with an aqueous solution of a basic aluminumcompound selected from the group consisting of sodium aluminate compoundselected from the group consisting of sodium aluminate and potassiumaluminate, at a pH in the range between about 5.5 and about 8.0 and atemperature in the range between about 20° C. and about 90° C., therebyforming a precipitate, (b) aging the precipitate at a temperatureranging from about 20° C. to about 90° C. for at least about 15 minutesat a pH ranging from about 11.0 to about 12.0, (c) washing theprecipitate, (d) mixing the precipitate with one or more solution(s)containing solubilized molybdate or dimolybdate salts and cobalt saltsand phosphoric acid in an amount of from about 0.2 to about 1.5 moles ofphosphorus per mole of molybdenum at a pH in the range between about 4.0and about 6.0 and a temperature in the range between about 25° C. andabout 100° C. until adsorption of the metal salts onto the gel issufficient to yield a final catalyst having from about 2.5% w to about4% w cobalt and from about 10% w to about 14% w molybdenum, (e)extruding the product of step (d), and (f) drying and calcining theproduct of step (e) at a temperature ranging from about 300° C. to about900° C.
 23. A process for preparing highly active hydrotreatingcatalysts having surface areas above about 300 m² /g and at least about80% of the pore volume in pores having diameters less than about 50 Å,which process comprises:(a) precipitating an aqueous solution of an acidaluminum salt selected from the group consisting of aluminum sulfate,aluminum nitrate and aluminum chloride, with an aqueous solution of abase at a pH in the range between about 5.5 and about 8.0 and atemperature in the range between about 20° C. and about 90° C., therebyforming a precipitate, (b) aging the precipitate at a temperatureranging from about 20° C. to about 90° C. for at least about 15 minutesat a pH ranging from about 11.0 to about 12.0, (c) washing theprecipitate, (d) mixing the precipitate with one or more solution(s)containing solubilized molybdate or dimolybdate salts and nickel salts,and phoshoric acid in an amount of from about 0.2 to about 1.5 moles ofphosphorus per mole of molybdenum at a pH in the range between about 4.0and about 6.0 and a temperature in the range between about 25° C. andabout 100° C. until adsorption of the metal salts onto the gel issufficient to yield a final catalyst having from about 2.5% w to about4% w nickel and from about 10% w to about 14% w molybdenum, (e)extruding the product of step (d), and (f) drying and calcining theproduct of step (e) at a temperature ranging from about 300° C. to about900° C.
 24. A process for preparing highly active hydrotreatingcatalysts having surface areas above about 300 m² /g and at least about80% of the pore volume in pores having diameters less than about 50 Å,which process comprises:(a) precipitating an aqueous solution of an acidaluminum salt selected from the group consisting of aluminum sulfate,aluminum nitrate and aluminum chloride with an aqueous solution of abase at a pH in the range between about 5.5 and about 8.0 and atemperature in the range between about 20° C. and about 90° C., therebyforming a precipitate, (b) aging the precipitate at a temperatureranging from about 20° C. to about 90° C. for at least about 15 minutesat a pH ranging from about 11.0 to about 12.0, (c) washing theprecipitate, (d) mixing the precipitate with one or more solution(s)containing solubilized molybdate or dimolybdate salts and cobalt salts,and phosphoric acid in an amount of from about 0.2 to about 1.5 moles ofphosphorus per mole of molybdenum at a pH in the range between about 4.0and about 6.0 and a temperature in the range between about 25° C. andabout 100° C. until adsorption of the metal salts onto the gel issufficient to yield a final catalyst having from about 2.5% w to about4% w cobalt and from about 10% w to about 14% w molybdenum, (e)extruding the product of step (d), and (f) drying and calcining theproduct of step (e) at a temperature ranging from about 300° C. to about900° C.
 25. A process for preparing highly active hydrotreatingcatalysts having surface areas above about 300 m² /g and at least about80% of the pore volume in pores having diameters less than about 50 Å,which process comprises:(a) titrating an aqueous solution of an acidwith aqueous solution of a basic aluminum compound selected from thegroup consisting of sodium aluminate and potassium aluminate at a pH inthe range between about 5.5 and about 8.0 and a temperature in the rangebetween about 20° C. and about 90° C., thereby forming a precipitate,(b) aging the precipitate at a temperature ranging from about 20° C. toabout 90° C. for at least about 15 minutes at a pH ranging from about11.0 to about 12.0, (c) washing the precipitate, (d) mixing theprecipitate with one or more solution(s) containing solubilizedmolybdate or dimolybdate salts and nickel salts, and phosphoric acid inan amount of from about 0.2 to about 1.5 moles of phosphorus per mole ofmolybdenum at a pH in the range between about 4.0 and about 6.0 and atemperature in the range between about 25° C. and about 100° C. untiladsorption of the metal salts onto the gel is sufficient to yield afinal catalyst having from about 2.5% w to about 4% w nickel and fromabout 10% w to about 14% w molybdenum, (e) extruding the product of step(d), and (f) drying and calcining the product of step (e) at atemperature ranging from about 300° C. to about 900° C.
 26. A processfor preparing highly active hydrotreating catalysts having surface areasabove about 300 m² /g and at least about 80% of the pore volume in poreshaving diameters less than about 50 Å, which process comprises:(a)titrating an aqueous solution of an acid with an aqueous solution of abasic aluminum compound selected from the group consisting of sodiumaluminate and potassium aluminate at a pH in the range between about 5.5and about 8.0 and a temperature in the range between about 20° C. andabout 90° C., thereby forming a precipitate, (b) aging the precipitateat a temperature ranging from about 70° C. to about 90° C. for at leastabout 15 minutes at a pH ranging from about 11.0 to about 12.0, (c)washing the precipitate, (d) mixing the precipitate with one or moresolution(s) containing solubilized molybdate or dimolybdate salts andcobalt salts, and a phosphoric acid in an amount of from about 0.2 toabout 1.5 moles of phosphorus per mole of molybdenum at a pH in therange between about 4.0 and about 6.0 and a temperature in the rangebetween about 25° C. and about 100° C. until adsorption of the metalsalts onto the gel is sufficient to yield a final catalyst having fromabout 2.5% w to about 4% w cobalt and from about 10% w to about 14% wmolybdenum, (e) extruding the product of step (d), and (f) drying andcalcining the product of step (e) at a temperature ranging from about300° C. to about 900° C.